The American Urological Association (the AUA) is outraged that the United States Preventive Services Task Force doesn’t support, has even “disparaged,” PSA screening. Dr. John Lynch, a member of its Board of Directors, even appealed to prostate cancer survivors to lobby against the Task Force’s recommendation, painting a dire picture of life without this controversial screening test:
“If we go back to the pre-PSA era, over two-thirds of the men we diagnose will have advanced prostate cancer and will be incurable and will die with terrible symptoms.”
His argument seems unassailable.
(1) Advanced prostate cancer → incurable
(2) Incurable cancer → die of terrible symptoms
(3) Die of terrible symptoms → bad situation!
I respect Lynch’s opinion. As a physician who has cared for men with advanced prostate cancer, and as a godson who lost his godfather to this terrible disease, I would love to prevent anyone from having to die of this illness. But we must be careful not to let Lynch’s dire picture cloud our vision of the true risks and benefits of PSA screening. Because the two-thirds figure he spouts is misleading. It ignores the disproportionate influence PSA screening has on the denominator of this population. Add enough people to the list of prostate cancer survivors, even people who wouldn’t have died of prostate cancer anyway, and you can improve on the two-thirds figure. But that doesn’t mean that you’ve improved anyone’s health. It is death from advanced prostate cancer that we need to reduce, not the percentage of prostate cancer patients who have advanced disease.
Imagine you live in a city where physicians don’t use the PSA test. Let’s say that three hundred men in this city are diagnosed with prostate cancer each year, one hundred with localized treatable disease and two hundred with advanced incurable illness. This situation leaves urologists like Lynch forlorn—2/3 of their patients are destined to die of their disease!
Now imagine that the city begins an aggressive screening campaign. And for the purposes of illustration, let’s pretend that this screening campaign does nothing to prevent prostate cancer deaths. Instead, it simply identifies men with localized cancers that would never have advanced anyway. Let’s propose that an additional seven hundred men are diagnosed with prostate cancer due to this screening strategy. This makes doctors like Lynch ecstatic—now a full 80% of their patients are diagnosed with curable disease. What an improvement. Instead of 2/3 of their patients dying, only 1/5 are beyond hope!
I have spoken with a number of prostate cancer experts since the Task Force guidelines came out. To a person, they all brought up the terribleness of the pre-PSA 2/3 figure. No doubt, it was awful to see such a high proportion of patients suffering from a fatal disease. But of course, increasing the denominator—adding a bunch of men with indolent cancers to the numbers—doesn’t necessarily do anything to improve patients’ lives. Indeed, it could cause the seven hundred men to experience burdensome treatments and to live with the fear of prostate cancer recurrence.
The goal of prostate screening is not to make urologists less downtrodden about their patients’ life expectancies. Nor is it to create business opportunities for prostate cancer specialists. The goal is to save lives. I expect that the PSA test does save lives, but not nearly as many as most urologists assume, and with many more men left to endure burdensome treatments for indolent tumors. We should not let Lynch’s statistics mislead us. As he points out in his statement: “Prostate cancer is still, despite our screening efforts, the second leading cause of male cancer deaths in the United States.”
Even with aggressive pre-PSA screening, in other words, many men still die of prostate cancer. We need to focus less on fuzzy math and more on developing better screening tests.
